This invention relates to a scooter lift for a vehicle and, in particular, to an improved external lift for loading and transporting a scooter safely.
A variety of small motorized scooters have been developed to carry a seated person through areas intended for pedestrian traffic. These scooters are battery powered, ride on either three or four small wheels, and are relatively compact but can be rather heavy because of the battery and electric motor. Unlike powered or unpowered wheelchairs, motorized scooters are usually not driven into a van or other vehicle with a person seated on the scooter. Rather, a lift is provided for attaching a scooter to the vehicle for traveling long distances. Such lifts are either external, as illustrated in U.S. Pat. No. 5,011,361 (Peterson) and U.S. Pat. No.5,567,107 (Bruno), or internal. External lifts typically have a fold-down platform for receiving a scooter. An internal lift is essentially a small derrick mounted in the rear portion of a van. This invention relates to an external lift having an improved load sensor and improved carriage.
External lifts typically include a horizontal square steel tube that fits within the receiver of a trailer hitch on a vehicle. A vertical post is welded to the tube and the rest of the lift is attached to the post in a series of joints. For example, an adjustable sleeve is attached to the vertical post to enable vertical adjustment of the platform. A lift mechanism is attached to the sleeve and to a horizontal hinge. The platform is attached to the movable part of the hinge, about which the platform rotates. There is a problem in that the joints flex or twist as loads are applied. The result is a constant rattling as one drives down the road, whether a scooter is loaded or not, particularly if not.
Any mechanical system subjected to vibration has a frequency at which energy is preferentially absorbed, i.e. a resonant frequency. It has been found that the combination of vehicle, lift, and scooter may have a resonant frequency at frequencies less than 10 Hz, particularly less than 1 Hz. Encountering the right source of vibration depends heavily upon the suspension of the vehicle and the type of road, which are difficult to predict. However, under rare but favorable conditions, a resonance can be set up that increases in amplitude enough to throw a scooter from a lift during transport, even with the hold-down typically used to clamp the scooter to the platform.
A problem with any external lift is the fact that, when loaded with a scooter, a considerable weight is being added a long distance behind the rear wheels of a vehicle. Particularly for smaller vehicles, wherein the weight of the scooter is a greater fraction of the total weight of the vehicle, any instability in the load adversely affects the handling of the vehicle. The effect is very much one of “the tail wagging the dog.” However picturesque the metaphor, the effect can be quite unsettling for a driver and, perhaps, unsafe.
It is known in the art to incorporate a load sensor into the platform, e.g. as disclosed in the Peterson patent. A problem with load sensors of the prior art is that the sensor is activated by a wheel of the scooter. Thus, the sensor is not just exposed to the elements but is exposed to dirt, stones, and whatever other debris may be adhering to the wheels of the scooter.
Another problem with sensors of the prior art is that the sensor mechanism includes a long coupling past the hinge about which the platform rotates. Because the sensor is located at or near ground level, in order for a wheel to roll over the sensor, the coupling mechanism is also exposed to dirt, mud, and damage. If the platform is lowered over uneven ground or ground strewn with rocks, twigs, or other debris, the treadle for the sensor may be supported and not depress when the wheel of a scooter rolls over the sensor. Finally, load sensors of the prior art typically sense a load at a small location. If a child stands on the lift, it is not likely that the child will stand on the load sensor. Thus, a child could actuate the lift and have the platform fold up with the child on it.
In view of the foregoing, it is therefore an object of the invention to provide an external scooter lift with a load sensor that senses a load anywhere on the scooter platform.
Another object of the invention is to provide a load sensor that is protected from the wheels of a scooter.
A further object of the invention is to provide a lift that minimizes motion of the platform during transport.
A further object of the invention is to minimize adversely affecting the handling of a vehicle loaded with an external scooter.
Another object of the invention is to prevent resonance effects in scooter lifts.
A further object of the invention is to secure a scooter to a lift even if the vehicle carrying the scooter is bounding down a road.